Researchers are embarking on a new frontier of biologically inspired machines. Development of a neuro-optical theory for practical robotic insect vision is taking shape. In this regard, some researchers are suggesting the use of optical compound eye sensors modeled after compound eyes found in insects. For example, see N. Franceschini et al., "From Insect Vision to Robot Vision," IEEE International Conference of Advanced Robotics (1991).
The compound eye in insects comprises a three dimensional multifaceted surface for receiving light. It is capable of sensing motion as well as rudimentary images. Making use of entomological terms, one facet is called an ommatidium, which literally means "little eye." Each ommatidium has a lens for receiving light therethrough, a crystalline cone connected to the lens, a group of photoreceptor cells near the vertex of the cone, and an adaptive pigment layer surrounding the cone. The adaptive pigment layer is dark during the daylight and is clear or translucent during the night. In essence, this layer adapts the eye to bright ambient light by optically isolating individual ommatidia. At low light levels, the layer becomes translucent allowing more light to travel throughout the system.
Evolution of compound eye vision has yielded five types of compound eye systems. See Nilsson D. E., "Vision Optics and Evolution," Bioscience, Vol. 39, No. 5, May, 1989. These five categories can be generalized into two classes based on how they physically gather and detect light: (1) neural superposition and (2) optical superposition. Further, a degenerative case of neural superposition is apposition. Moreover, optical superposition covers refracting, reflecting, and parabolic superposition eyes. Each eye type (1) and (2) uses a different light gathering strategy to separate or combine image information, while it is still in photonic form. The physical difference is that a neural superposition eye does not attempt to form an optical image by combining light from neighboring ommatidia. In contrast, each ommatidium in the optical superposition eye combines image forming light rays from neighboring ommatidia to form images or partial images. To summarize, the optical eye combines light into an optical image, whereas the neural superposition eye (including apposition eye) must process light inputs to form a neural image because there is no optical image formed.
While it has been recognized that artificial compound eyes would be advantageous in the robotics environment and elsewhere, there are no feasible systems and methods for inexpensively constructing reliable compound eyes or artificial ommatidia.